MICRO-HYDRO TECHNOLOGY

Flowing water contains energy. Micro-hydro systems were developed to extract this energy in the form of mechanical power, most often used to generate electricity. The amount of power available from flowing water depends both on the amount of water and the speed at which it is flowing, which in turn depends on the height (head) from which it is coming. Unlike large-scale hydro, Micro-hydro is designed to adapt existing streams rather than use large dams to manage water flow. Micro-hydro technology is only effective if the turbine is located close to the demand.

The term "micro-hydro" is usually used for power outputs of between 5 kW and 100 kW. Systems less than 5 kW are usually termed "pico-hydro" and are usually used for individual homes or communities of two or three houses.

Micro-hydro systems have the following components:

• A water turbine converts the energy in flowing or falling water into mechanical energy. The mechanical energy drives a generator, which produces electrical power.
• A control mechanism provides stable electrical power.
• Electrical transmission lines deliver the power to its destination.

Depending on the site, the following may be needed to develop a micro-hydropower system:

• An intake or weir to divert stream flow from the water course
• A canal/pipeline to carry the water flow from the intake to the forebay
• A forebay tank and trash rack to filter debris and prevent it from being drawn into the turbine at the penstock pipe intake
• A penstock pipe to convey the water to the powerhouse
• A powerhouse, in which the turbine and generator convert the power of the water into electricity
• A tailrace through which the water is released back to the river or stream

To determine a site's suitability for a micro-hydro system, a site assessment should be performed. Accurate assessments of head and flow, as well as measuring for infrastructure components, should be performed to determine project feasibility. Four key site characteristics should be determined: head, flow, pipe length and wire run.

Trends

Technology that has significantly reduced costs of micro-hydro include electronic load controllers (around since the mid80s, but much improved since their introduction), brushless exciters, composite turbine runners, plastic pipe capable of acting as pressure pipe (HDPE and PVC) and improved efficiency.

Resources

Micro-Hydropower Systems – A Buyer's Guide (Natural Resources Canada)

Equipment supply store that offers online courses and good definitions

BC Hydro definitions and summary

Small hydro atlas (summaries for various countries throughout the world)

Good collection of information, case studies around the globe